CMP Polishing Liquid Composition for Selectivity and Slurry Stability
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Solution Overview
Problem
In semiconductor manufacturing, particularly during the CMP process for STI formation, there is a challenge in achieving high polishing selectivity of insulating materials with respect to stopper materials while maintaining storage stability of polishing liquids, and in preventing excessive polishing that leads to surface irregularities and reduced flatness.
Innovation Solution
A polishing liquid containing abrasive grains, a specific copolymer derived from styrene and acrylic acid, and a pH-adjusted medium, which improves polishing selectivity and storage stability by controlling the pH between 4.5 and 7.5, and includes a water-soluble polymer and a phosphate compound to enhance dispersibility and prevent aggregation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional polishing liquid is used to improve polishing selectivity of insulating material with respect to stopper material, then the polishing selectivity is improved, but the storage stability deteriorates due to aggregation of abrasive grains
Solution Approach 1:
The patent introduces a specific copolymer as an intermediary substance between the abrasive grains and the liquid medium. This copolymer, containing both hydrophilic groups (carboxyl, hydroxyl, or amine groups) and hydrophobic groups (aromatic hydrocarbon groups), acts as a mediator that prevents aggregation of abrasive grains while maintaining polishing selectivity. The copolymer adsorbs onto the abrasive grain surfaces and provides steric stabilization, resolving the contradiction between achieving high polishing selectivity and maintaining storage stability.
Solution Approach 2:
The patent changes the chemical parameters of the polishing liquid by specifying a copolymer with particular compositional parameters: 1-50 mol% styrene component, 1-40 mol% aromatic hydrocarbon component, and specific hydrophilic group content (0.1-10 mmol/g). By optimizing these compositional parameters, the polishing liquid achieves both high polishing selectivity (through controlled adsorption on different materials) and storage stability (through prevention of grain aggregation via steric stabilization).
2Manufacturing precision
If polishing is performed to control the amount of insulating material removed, then the polishing degree is controlled by stopping when the stopper is exposed, but excessive polishing of the stopper occurs leading to surface irregularities
Solution Approach 1:
The patent applies the principle of local quality through the copolymer's differential adsorption behavior. The copolymer selectively adsorbs onto specific material surfaces (insulating material vs. stopper material) with different affinities, creating locally different polishing conditions. This selective adsorption creates a protective layer on the stopper surface that prevents excessive polishing, while allowing controlled removal of insulating material, thus eliminating surface irregularities.
Solution Approach 2:
The patent implements a feedback mechanism through the copolymer's real-time adsorption response during polishing. As the polishing process progresses and different materials are exposed, the copolymer dynamically adjusts its adsorption distribution, providing immediate feedback control over the polishing rate. This prevents over-polishing of the stopper by automatically reducing the mechanical action on exposed stopper surfaces through increased copolymer adsorption.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively enhances polishing selectivity, suppresses excessive polishing of both stopper and insulating materials, and maintains high flatness without dependence on pattern density, while ensuring storage stability and preventing aggregation of abrasive grains.
Implementation Method 1
the copolymer has a structure unit derived from at least one styrene compound selected from the group consisting of styrene and a styrene derivative and a structure unit derived from acrylic acid
Implementation Method 2
the pH of the polishing liquid is more than 4.5
Implementation Method 3
the polishing liquid is required to hardly change in properties such as aggregation between the abrasive grains in the case of long-term storage
Implementation Method 4
a phosphate compound to enhance dispersibility and prevent aggregation
Data Source
AI summary
An aspect of the present invention is a polishing liquid containing abrasive grains, a copolymer, and a liquid medium, in which the copolymer has a structure unit derived from at least one styrene compound selected from the group consisting of styrene and a styrene derivative and a structure unit derived from acrylic acid, a content of the copolymer is more than 0.01% by mass and 0.2% by mass or less based on the total amount of the polishing liquid, and a pH of the polishing liquid is more than 4.5.